Dynamic Ports

Add port to selected nodes:

Double-click in the diagram background in order to add a new node there.
Add ports to a selected node by clicking the above buttons or by using the context menu.
Draw links between ports by dragging between ports.
Right-click on a port to bring up menu.

Diagram Model saved in JSON format:

{ "class": "go.GraphLinksModel",
  "copiesArrays": true,
  "copiesArrayObjects": true,
  "linkFromPortIdProperty": "fromPort",
  "linkToPortIdProperty": "toPort",
  "nodeDataArray": [
{"key":1, "name":"Unit One", "loc":"101 204",
 "leftArray":[ {"portColor":"#fae3d7", "portId":"left0"} ],
 "topArray":[ {"portColor":"#d6effc", "portId":"top0"} ],
 "bottomArray":[ {"portColor":"#ebe3fc", "portId":"bottom0"} ],
 "rightArray":[ {"portColor":"#eaeef8", "portId":"right0"},{"portColor":"#fadfe5", "portId":"right1"} ] },
{"key":2, "name":"Unit Two", "loc":"320 152",
 "leftArray":[ {"portColor":"#6cafdb", "portId":"left0"},{"portColor":"#66d6d1", "portId":"left1"},{"portColor":"#fae3d7", "portId":"left2"} ],
 "topArray":[ {"portColor":"#d6effc", "portId":"top0"} ],
 "bottomArray":[ {"portColor":"#eaeef8", "portId":"bottom0"},{"portColor":"#eaeef8", "portId":"bottom1"},{"portColor":"#6cafdb", "portId":"bottom2"} ],
 "rightArray":[  ] },
{"key":3, "name":"Unit Three", "loc":"384 319",
 "leftArray":[ {"portColor":"#66d6d1", "portId":"left0"},{"portColor":"#fadfe5", "portId":"left1"},{"portColor":"#6cafdb", "portId":"left2"} ],
 "topArray":[ {"portColor":"#66d6d1", "portId":"top0"} ],
 "bottomArray":[ {"portColor":"#6cafdb", "portId":"bottom0"} ],
 "rightArray":[  ] },
{"key":4, "name":"Unit Four", "loc":"138 351",
 "leftArray":[ {"portColor":"#fae3d7", "portId":"left0"} ],
 "topArray":[ {"portColor":"#6cafdb", "portId":"top0"} ],
 "bottomArray":[ {"portColor":"#6cafdb", "portId":"bottom0"} ],
 "rightArray":[ {"portColor":"#6cafdb", "portId":"right0"},{"portColor":"#66d6d1", "portId":"right1"} ] }
 ],
  "linkDataArray": [
{"from":4, "to":2, "fromPort":"top0", "toPort":"bottom0"},
{"from":4, "to":2, "fromPort":"top0", "toPort":"bottom0"},
{"from":3, "to":2, "fromPort":"top0", "toPort":"bottom1"},
{"from":4, "to":3, "fromPort":"right0", "toPort":"left0"},
{"from":4, "to":3, "fromPort":"right1", "toPort":"left2"},
{"from":1, "to":2, "fromPort":"right0", "toPort":"left1"},
{"from":1, "to":2, "fromPort":"right1", "toPort":"left2"}
 ]}